BACKGROUND AND
OBJECTIVES: The objective of this study was to compare the quality and safety
of retrobulbar block for the treatment of cataracts by phacoemulsification using
needles of different sizes: 27 × 0.70 mm and 20 × 0.55 mm.METHODS: Candidates for ophthalmic block for the treatment of cataracts
by phacoemulsification were selected prospectively. After sedation and standardized
monitoring, a retrobulbar block with 4 mL of 1% ropivacaine containing hyaluronidase
was performed with a single inferolateral puncture. In Group I (GI), the 25
× 0.70 mm needle was used, while in Group II (GII) a 20 × 0.55 mm
needle was used. All patients had a CT scan at the time of the blockade and
five minutes after the administration of the anesthetic solution with radiologic
contrast. Ocular mobility was assessed after three, five, and ten minutes. The
incidence of complications in both groups and the satisfaction of patients and
surgeons were compared by applying a standardized questionnaire.RESULTS: Fifty-four adult patients were evaluated (27 per group). Patients
did not complain of intraoperative pain or perception of light. The anesthetic
procedure was considered very good (VG) or excellent (E) in 96.3% of the cases
in both groups. All patients were subjected to the same assessment. The need
of block repetition between both groups did not differ (p = 1.0). Patients in
GI showed decreased ocular mobility at 3 minutes (p = 0.03). The intraconal
retrobulbar placement of the needle was observed on both groups. Anesthetic
dispersion at 5 minutes was similar in the two groups.CONCLUSIONS: Retrobulbar block with a single inferolateral puncture with
a 20 × 0.55 mm needle, using low doses of anesthetics, is an effective
and safe option for the treatment of cataracts by phacoemulsification.

Cataracts are the
main cause of reversible blindness in the world 1. Its treatment
consists of the surgical removal of the opaque lens, which is substituted by
an intraocular lens. A successful surgery requires anesthetic procedure with
adequate analgesia, providing comfort and safety. Despite the development of
new techniques such topical, intracameral, and sub-Tenon's block 2,
ophthalmic blocks are still widely used 3. A variable terminology
is used for ophthalmic blocks. In the present study we use the expression retrobulbar
block because the authors consider that in the techniques described below the
tip of the needle is always placed behind the eye globe.

A consensus on
the ideal needle length for those blocks does not exist. To improve safety without
the loss of quality it has been suggested that the needle should not be introduced
more than 30 mm inside the eye chamber. Van den Berg (2004) considers the 25
mm long needle more adequate 5 despite the complications described
in the literature 6,7. Smaller needles are considered less traumatic;
however, there are reports of a greater incidence of failed blocks with those
needles, which does not stimulate their routine use 5.

The primary objective
of this study was to compare the quality and safety of the retrobulbar block
with a small volume of anesthetic using 25 × 0.7 mm or 20 × 0.55
mm needles for the treatment of cataracts by phacoemulsification. Secondary
objectives included: 1 - to evaluate the final position of the needle in the
eye chamber, therefore contributing for a more adequate terminology; and 2 -
to observe the dispersion of the anesthetic in the eye chamber.

METHODS

This is a prospective,
comparative, randomized, double-blind study.

After approval
by the Ethics Committee of the Hospital das Clínicas da Universidade
Federal de Goiás and signing of the informed consent, patients with surgical
indication of phacectomy by phacoemulsification with implantation of intraocular
lens at the Centro de Referência em Oftalmologia of the Universidade Federal
de Goiás (CEROF-UFG) were enrolled in this study. Only one eye of each
patient was included in the study. Patients with monocular vision, any changes
in eye mobility (e.g., strabismus, paralysis), history of past ophthalmologic
surgery, with contraindications for ophthalmologic block under sedation, and
history of allergy to iodine-containing contrast were excluded from the study.
The same professional, one of the authors of this report (HMC), performed all
blockades.

All study patients
underwent echobiometry with an Ocusan I (Alcon Labs, Fort Worth, TX, USA) echobiometer
to determine the intraocular lens to be implanted and to measure the axial length
of the eye.

The anesthetic
technique consisted of standard monitoring, including pulse oximetry (SpO2),
continuous cardioscopy, and non-invasive blood pressure (NIBP). After peripheral
venipuncture (22G catheter), D5W solution was administered, followed by the
administration of oxygen, 2 L.min-1 via nasal catheter. Patients
were sedated with fixed doses of diazepam (2.5 mg) and fentanyl (25 µg),
and fractionated doses of propofol until the loss of response to verbal commands.
After antisepsis with topical povidine and removal of excess anti-septic solution,
retrobulbar block was performed with a single puncture, modified inferolateral
8. In this technique, the needle is introduced with mild pressure
on the inferior border of the bony orbit at the level of the inferior eyelid
(Figure 1), perpendicular to the skin for the first 10 mm
and, after a slight superomedial inclination, the rest of the needle was introduced
until its hub touched the skin.

An anesthetic solution
containing 1% ropivacaine and hyaluronidase (50 IU.mL-1) with a total
fixed volume of 4 mL was injected at 0.5 mL.sec-1. Intermittent compression
of the ocular angle and inferior orbital border was applied for three minutes
without direct compression of the globe (Figure 2) to facilitate
the dispersion of the anesthetic solution and prevent it from depositing in
the anterior portion of orbit. Patients were randomly divided into two groups:
in Group I (GI), a 25 × 0.75 mm needle was used, and in Group II (GII)
a 20 x 0.55 mm needle was used. One patient in each group was randomly selected
for the administration of 0.5 mL of the water soluble iodine-containing contrast
media (Iohexol - 300 mg.mL-1) mixed with the anesthetic solution.
Those patients had a computed tomography (MDCT) at the time of the anesthetic
procedure when the needle was fully inserted to determine the position of the
tip. A second MDCT was done five minutes after the injection of the contrast-containing
anesthetic solution to observe its dispersion. The exam was done by a 6 channels
Multiple Detector - Somaton Emotion (Siemens) CT scanner. Images were reconstructed
by an specific software (Viewer Sinet Siemens) on axial, coronal, and oblique
sagittal with continuous acquisitions of 0.6 mm. Images were analyzed by one
of the authors of this report, a radiologist (KIST).

Three minutes after
the administration of the anesthetic solution, a drop of antiseptic solution,
1% povidone iodine, was applied to the eye to be operated and the patient was
questioned whether he/she felt pain or not, in order to evaluate the sensitivity
to pain of the anesthetized eye.

Ocular mobility
was evaluated on moments zero (before the anesthetic procedure), 3, 5, and 10
minutes. The four recti muscles of the eye and levator palpebrae superioris
muscle were evaluated individually, establishing scores according to the ocular
mobility of each muscle: 2 for normal mobility, 1 for decreased mobility, and
0 (zero) for muscular akinesia (total score varied from 0-10). The surgery was
performed when the patient presented a score of 0 (zero). If at 3 minutes the
patient presented a score other than 0 (zero), he/she was evaluated again at
5 minutes, when the surgery was performed if the total score < 3,
or a supplementary block was done with the same needle used for the first puncture,
in the supero-medial position, with 2 mL of the anesthetic solution if the score
were > 3. In those cases, ocular mobility was evaluated again at 10 minutes,
at which time the surgery was performed.

Surgeries were
performed by physicians of the Ophthalmology Department of the CEROF-UFG who
were not aware of the anesthetic technique used. Patients were followed by the
outpatient clinic of the same institution until their discharge.

The incidence of
ocular and systemic complications in both groups was compared. The level of
patient and surgeon satisfaction was evaluated by a standardized questionnaire.
All evaluations of this study were done by a single evaluator who was not aware
of the group distribution.

The software SPSS
11.5 (SPSS Inc., Chicago, IL, USA) was used for the statistical analysis. The
Chi-square test was used to compare categorical data. The independent Student
t test was used to analyze parametric data and the Mann-Whitney U test
was used for non-parametric data. A level of 5% (p < 0.05) was considered
statistically significant.

RESULTS

Fifty-four adult
patients, 27 in each group, with a mean age of 65.41 ± 11.41 years, in
Group I (GI), and 67.55 ± 9.87 years, in Group II (GII) (p = 0.4), were
enrolled in this study. Both groups did not show statistically significant differences
regarding gender, age, weight, physical status according to the American Society
of Anesthesiologists (ASA), axial length of the eye, and the side to be operated
(Table I). The mean dose of propofol administered in GI
was 27.4 ± 5.0 mg and in GII was 26.4 ± 4.1 mg (p = 0.4). At the
end of the surgery patients did not complain of intraoperative pain or light
perception. All patients in this study would undergo the same anesthetic procedure
if they needed another ophthalmologic surgery (Table II).
Surgeon satisfaction with the anesthetic technique was deemed very good (VG)
or excellent (E) in 26 patients in GI (96.29%) and in 26 patients in GII (96.29%;
p = 1.0). The procedure was considered VG or E by 100% of the patients. Surgeries
were done with a single puncture, without supplementation with a second puncture,
in 26 patients in GI (96.29%) and in 25 patients in GII (92.59%; p = 1.0). Ocular
or systemic complications were not observed in this study. Patients in both
groups did not complain of pain after the instillation of 1% povidone iodine
at 3 minutes. Ocular mobility (Table III) was similar in
both groups at all times, and only at three minutes a difference for the median
was observed. Patients in GI showed the lower ocular mobility at three minutes
(0.6 ± 1.1 vs. 1.3 ± 1.4, p = 0.03). Ocular mobility in
both groups at 5 and 10 minutes was not statistically significant. Considering
an alpha error of 0.05 and the differences to be detected between both groups
equal to one, the statistical tests done in the present study achieved a power
of 95%.

Images obtained
by the MDCT in GI showed the tip of the needle in the retrobulbar intraconal
space and the dispersion of contrast-containing anesthetic solution was preferentially
periocular and intraconal (Figures 3, 4,
5, and 7). The tip of the needle in
GI (25 × 0.7 mm) reached a 32-cm depth in the orbital cavity.

Multiple detector
CT images in GII also showed clearly the retrobulbar intraconal placement of
the 20 x 0.55 mm needle, at a 22 mm depth in the orbital cavity. Dispersion
of the anesthetic solution in this group was also predominantly periocular and
intraconal (Figures 7, 8, 9,
and 10).

DISCUSSION

The progressive
increase in the number of ocular surgeries makes the ophthalmic block the most
common anesthetic technique performed nowadays. Patients undergoing cataract
treatment are usually elderly and frequently have associated systemic diseases
and, for this reason, benefit from locoregional blocks associated or not with
sedation 9. In this technique, besides the sensitive blockade, adequate
control of ocular mobility provided by paralysis of extrinsic eye muscles through
blockade of the oculomotor, trochlear, and abducens nerves, located behind the
globe, is also desirable.

In retrobulbar
intraconal block the local anesthetic is injected inside the muscular cone (space
where the optic nerve, most motor and sensitive ocular nerves, and adnexa are
located 10), by the percutaneous or transconjunctival approach. It
has the advantage of providing fast onset of analgesia and akinesia using a
small volume of anesthetic. However, complications caused by inserting the needle
in the intraconal space, such as retrobulbar hemorrhage, trauma of the optic
nerve, perforation of the sclera, stimulation of the oculocardiac reflex, spread
of the anesthetic agent to the central nervous system through the sheath of
the optic nerve, meningeal irritation, and optic atrophy have been described
11-13.

Peribulbar block
(PB) initially described by Davis and Mandel 14 consists of injecting
the anesthetic in the extraconal space. It guarantees ocular stability and anesthesia
during surgery, and it is considered by many a safer option than the retrobulbar
intraconal block (RBIB). Most common, although rare, complications include periocular
and retrobulbar hemorrhage, increase in intraocular pressure, depression of
the central nervous system, perforation of the globe, and incomplete anesthesia
and akinesia 15,16. It also has a late onset of action and needs
larger volumes of anesthetic 9.

Van Den Berg (2004)
5 classified this anesthesia according to the place the anesthetic
solution was deposited: circumocular (sub-Tenon's or episcleral), periocular
(anterior, superficial), periconal (posterior, deep), and apical (ultra-deep).
The author concluded that the efficacy of this anesthetic technique depends
on depositing the anesthetic close to the orbital apex. Since ophthalmic blocks
are done without direct visualization of the tip of the needle, there are doubts
on whether, occasionally, the retrobulbar intraconal block is achieved instead
of the desired extraconal block 4,17,18, justifying the good quality
of the anesthesia with small volumes even when using the extraconal technique.

A consensus on
the ideal needle length for ophthalmic block has not been achieved. Some authors
5,19 consider the 25 mm long needle more adequate, stating that smaller
needles would increase the need to repeat the blockade while longer needles
would be associated with an increase in the rate of complications, without improving
the quality of anesthesia 5. Others consider needles with less than
25 mm satisfactory and associated with reduced risk, but they consider to be
performing a peribulbar block 20,21.

The present study
does not support the notion that the use of 25 mm or longer needles are necessary
for a RBIB of good quality. The incidence of repetition of the blockade in ophthalmic
blocks using the 20 × 0.55 mm needles was not increased when compared
with the 25 × 0.7 mm needles (3.7% vs. 7.4%, p = 1.0), and it was
lower than reported in the literature (10% to 33%) 5. Currently,
the success of anesthesia provided by ophthalmic blocks has been proportional
to the experience of the anesthesiologist and adequate knowledge of the local
anatomy, regardless of the name chosen, peribulbar block or retrobulbar block
4,9. Despite the controversy regarding the terminology of ophthalmic
blocks, MDCT images demonstrated clearly that an intraconal retrobulbar block
was performed using the technique described with 25 × 0.7 mm or 20 ×
0.55 mm needles.

Approximately 96%
of the surgeons and 100% of the patients in both groups considered the technique
very good (VG) or excellent (E). Patients did not complain of intraoperative
pain or uncomfortable visual sensation. Subjective evaluation, both by surgeons
and patients, was adequate and similar in both groups. This was reflected on
the fact that all patients would undergo the same anesthetic technique in the
future if they needed an ophthalmologic surgery.

The results of
the present study demonstrated similar latency of the sensitive blockade in
both groups (p = 1.0). However, at three minutes the motor blockade was greater
when the 20 x 0.55 mm needle was used than the 25 × 0.7 mm needle, but
it was the same at 5 minutes (p = 0.08). One can hypothesize that a small volume
of the local anesthetic was deposited in the anterior portion of the retrobulbar
intraconal space when using the 20 × 0.55 mm needle. The periocular placement
of the local anesthetic would provide adequate pain control since the innervation
of the eye globe penetrates in its posterior pole. To reach the motor innervation
of the eye the anesthetic solution would have to disperse to the posterior portion
of the intraconal space where the nerves are close together. But at 5 minutes
both groups have similar results for all the parameters analyzed, demonstrating
equivalence in the objective assessment of the blockade.

Although patients
were not monitored with direct tests (e.g., retinal mapping, ultrasound) to
detect possible complications, such as ocular perforation, careful clinical
evaluation, including complaints of the patients (e.g., scintillating scotomas,
blurred vision) did not suggest the development of complications.

Multiple detector
CT images reinforced the clinical observations. It was demonstrated that the
needle was advanced beyond the equatorial axis of the globe, characterizing
a RBB, as predicted by the authors. In GI, the needle penetrated deeper in the
orbital cavity than in GII, resting closer to the orbital apex, where the motor
nerves of the eye are grouped together. It was also observed, in both groups,
that the needle was placed inside the muscular cone, with similar dispersion
of the anesthetic solution, which could justify the similarity in the quality
of anesthesia in GI and GII.

Retrobulbar block
with the 20 × 0.55 mm needle can be considered a safer option without
losing quality when compared to the 25 × 0.70 mm, using the inferolateral
approach for the treatment of cataracts by phacoemulsification. Assuming that
the rate and severity of complications is proportional to the length of the
needle, one can suggest the routine use of the 20 × 0.55 mm needles for
ophthalmologic blockades in those procedures.

Multiple detector
CT images demonstrated that in the anesthetic technique described here the tip
of the needle can be placed beyond the equatorial axis of the globe, and that
it can even be intraconal, using both the 25 × 0.7 mm and 20 × 0.55
mm needles, justifying the terminology of retrobulbar block (RB).

The contrast-containing
anesthetic solution showed periocular and intraconal dispersion in both groups,
as demonstrated by the MD-CT.

Further studies
are necessary to evaluate the efficacy of anesthesia with the technique described
here, with the 20 × 0.55 mm needle, for other types of ophthalmologic
surgeries. This study, using MD-CT images during ophthalmologic blocks for treatment
of cataracts, is part of a research line that includes the evaluation of relationship
between needles used for blockades and orbital structures, contributing for
more detailed knowledge of this anesthetic technique and less aggressive and
more effective blocks, without the loss of efficacy.